1. Field of the Invention
The present invention relates to a telecommunications system; and more specifically to a communication timing control apparatus for use in a node included in a telecommunications network for controlling with accuracy a timing at which data are transmitted. The invention also relates to a method of controlling the timing.
2. Description of the Prior Art
As systems for allowing a plurality of spatially distributed nodes to transmit and receive data without any collision, available are the time division multiple access (TDMA) system and the carrier sense multiple access (CSMA) system, such as a CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) system and a CSMA/CD (Carrier Sense Multiple Access with Collision Detection) system, as taught in Y. Matsushita, et al., “Wireless LAN Architecture”, pp. 47, 53-59 and 69, Kyoritsu Shuppan Co., Ltd., Tokyo, Japan, 1996.
In accordance with the CSMA system, a node, intending to transmit data, determines whether or not any other node is in communication by sensing a carrier or frequency, and then transmits the data when having determined that the other nodes are not in communication. However, one of the problems with the CSMA systems is that the number of channels available for communication at the same time is remarkably limited.
The TDMA system allots a particular time slot to each of a plurality of nodes so as to cause each node to transmit data only in the time slot allotted thereto, and allows the number of channels available for communication at the same time to be increased more easily than the CSMA system. When nodes expected to communicate with each other dynamically change, a certain node plays the role of a central or management node for dynamically allotting time slots to the other nodes.
However, the TDMA system has a drawback that, when the central node expected to allot time slots malfunctions, the entire telecommunications system goes down. Further, the TDMA system must dynamically reallot a particular time slot to each node by a sophisticated procedure, and is therefore likely to fail to rapidly adapt to the varying environment. In addition, the TDMA system is unable to vary the width of a time slot itself.